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| Titel |
GNSS troposphere tomography based on two-step reconstructions using GPS observations and COSMIC profiles |
| VerfasserIn |
P. Xia, C. Cai, Z. Liu |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 31, no. 10 ; Nr. 31, no. 10 (2013-10-24), S.1805-1815 |
| Datensatznummer |
250086131
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| Publikation (Nr.) |
 copernicus.org/angeo-31-1805-2013.pdf |
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| Zusammenfassung |
| Traditionally, balloon-based radiosonde soundings are
used to study the spatial distribution of atmospheric water vapour. However,
this approach cannot be frequently employed due to its high cost. In
contrast, GPS tomography technique can obtain water vapour in a high temporal
resolution. In the tomography technique, an iterative or non-iterative
reconstruction algorithm is usually utilised to overcome rank deficiency of
observation equations for water vapour inversion. However, the single
iterative or non-iterative reconstruction algorithm has their limitations.
For instance, the iterative reconstruction algorithm requires accurate
initial values of water vapour while the non-iterative reconstruction
algorithm needs proper constraint conditions. To overcome these drawbacks,
we present a combined iterative and non-iterative reconstruction approach
for the three-dimensional (3-D) water vapour inversion using GPS observations
and COSMIC profiles. In this approach, the non-iterative reconstruction
algorithm is first used to estimate water vapour density based on a priori
water vapour information derived from COSMIC radio occultation data. The
estimates are then employed as initial values in the iterative
reconstruction algorithm. The largest advantage of this approach is that
precise initial values of water vapour density that are essential in the
iterative reconstruction algorithm can be obtained. This combined
reconstruction algorithm (CRA) is evaluated using 10-day GPS observations in
Hong Kong and COSMIC profiles. The test results indicate that the water
vapor accuracy from CRA is 16 and 14% higher than that of iterative
and non-iterative reconstruction approaches, respectively. In addition, the
tomography results obtained from the CRA are further validated using
radiosonde data. Results indicate that water vapour densities derived from
the CRA agree with radiosonde results very well at altitudes above 2.5 km.
The average RMS value of their differences above 2.5 km is 0.44 g m−3. |
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